1. Field of the Invention:
The present invention relates to a linear guide apparatus having a protector for protecting a dust seal.
2. Description of the Prior Art:
Generally, a linear guide apparatus, as shown in FIG. 9, includes a guide rail 1 extending in an axial direction and a slider 2 slidably straddling the guide rail 1. A ball rolling groove 3 having a semi-circular cross section and extending axially is formed in each of both side surfaces of the guide rail 1. The slider 2 has ball rolling grooves (not shown) formed in inner surfaces of both side walls 4 so that the ball rolling grooves of the slider 2 respectively oppose the ball rolling grooves 3 of the guide rail 1.
Many balls are rollably mounted between the corresponding ball rolling grooves of the guide rail 1 and the slider 2, and the slider 2 is moved axially on the guide rail 1 through the rolling of the balls. With the movement of the slider 2, the balls interposed between the guide rail 1 and the slider 2 are moved to an end of a slider main body 2A of the slider 2. In order to continuously move the slider 2, it is necessary to circulate the balls.
Thus, a ball return path (not shown) is formed in each of the side walls 4 of the slider main body 2A penetrating in the axial direction and, further, end caps 5 are attached to opposite ends of the slider main body 2A so that a ball circulating path is formed by bringing the ball return path in communication with a U-shaped connecting path formed in each of the end caps 5. Furthermore, since smooth rolling of the balls is disturbed when foreign matters, such as dust, cuttings, and the like, are deposited on the upper surface of the guide rail 1 or on the ball rolling grooves 3 in both sides of the guide rail 1, a dust seal 10 is usually attached as a wiper to each of the end caps 5.
Furthermore, reference numeral 12 in FIG. 9 designates a grease fitting threaded into the end cap 5.
The dust seal 10 is comprised of a metallic plate and a rubber member bonded to a front surface of the metallic plate. The rubber member has lip portions whose tip end forms an acute angle with the metallic plate. Cuttings of a large size or foreign matter such as weld sputters which are easily deposited on the guide rail 1 tend to intrude into the interior of the slider 2 by deforming or breaking the lip portions of the dust seal 10. In particular, a recess 3a for a wire retainer is formed in the bottoms of the ball rolling grooves 3 of the guide rail 1, and it is difficult to interrupt the intrusion of the foreign matter through the recess 3a by the weak projections of the lip portions.
Accordingly, as a countermeasure, a scraper having a minute clearance between the outer surface of the guide rail 1 is mounted on a forward surface of a rubber wiper. A linear guide apparatus having such a scraper is disclosed in Japanese Utility Model Laid-Open Publication No. 63-121815.
However, the scraper in the prior art linear guide apparatus mentioned above involves a problem in that since the scraper is attached to the forward (in a direction of movement) end surface of the rubber wiper closely in contact therewith, although cuttings of a large size are removed by the scraper, when hot weld sputters are deposited, the heat of the weld sputters is easily conducted to the rubber wiper causing the rubber wiper to be burned.
Moreover, since there is no backing member attached to the rear surface of the rubber wiper to support the weak and small lip portions, foreign matter which have passed through the clearance between the scraper and the guide rail will intrude into the interior of the slider by pushing the lip portions of the rubber wiper upwardly. Therefore, there is a problem in that in an adverse environment wherein a large amount of cuttings are generated, it is difficult to keep a useful service life of the linear guide apparatus, or to extend a maintenance interval or to achieve a maintenance-free service life.